Processes for the preparation of 5-cyanovaleric acid from pentenenitriles by carbonylation in the presence of cobalt carbonyl catalysts are known. See, for example, U.S. Pat. No. 4,508,660 to Sieja where the reaction is carried out in a sulfone solvent, and U.S. Pat. No. 4,060,543 to Weitz, et al., where the reaction is carried out in the presence of basic heterocyclic compounds having a 5-membered or 6-membered nitrogen-containing ring, for example pyridine.
Wadden et al., British Patent 1,497,046, disclose a process for the manufacture of cyano-substituted aliphatic carboxylic esters which comprises reacting an alkenenitrile having at least 3 carbon atoms in the alkene residue with carbon monoxide and an alcohol under pressure in the presence of a catalyst. The reaction is preferably carried out in the presence of a weak organic base or of certain other compounds which function as Lewis bases, including pyridine, N-alkylpyrrolidones and caprolactam. Such compounds may comprise, for example, from 5 to 50% by weight of the reaction mixture.
It seems to be recognized in the art that the presence of pyridine, or certain substituted pyridines, in a carbonylation reaction mixture provides an increased yield in the straight chain isomers--See, for example: Organic Chemistry and Technology, New Method of Production of Adipic Acid, N. S. Imyanitov and E. N. Rakhlina, Khimicheskaya Promyshlennost, Vol. 19, No. 12, pp. 4-7. 1987; Chem. Ztg. 111 no 11:317-23 (1987) Hydrocarboxylation of Unsaturated Carboxylic Acids and Esters with Cobalt Carbonyl/Pyridine Complex Catalyst Systems by Bernhard Fell, Institute for Technical Chemistry and Petrochemistry of the RWTH Aachen, and Zilin Jin, Dalian Institute of Technology, Dalian/Peoples Republic of China; and New Syntheses with Carbon Monoxide, edited by J. Falbe, page 252, Springer-Verlag, Berlin, Heidelberg, New York, 1980.